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IE branch

This code uses object/feature detection to determine which way to go. Because Internet Explorer on

Windows is the only browser that supports the

ActiveXObject

class, that is a fair way to test for IE. The

second test is a generic one determining if the browser supports the DOM standard

createDocument()

method. Even though Mozilla is the only browser that currently supports this, it’s conceivable that other

browsers may adopt this functionality in the future, so testing in this way makes the code future-proof. If

neither statement evaluates to

true

, then the constructor throws an error indicating no XML DOM object

is available.

The IE branch

For the IE section of the constructor, just insert the code from the

createXMLDOM()

function earlier in

the chapter:

function XmlDom() {

if (window.ActiveXObject) {

var arrSignatures = [“MSXML2.DOMDocument.5.0”, “MSXML2.DOMDocument.4.0”,

“MSXML2.DOMDocument.3.0”, “MSXML2.DOMDocument”,

“Microsoft.XmlDom”];

for (var i=0; i < arrSignatures.length; i++) {

try {

var oXmlDom = new ActiveXObject(arrSignatures[i]);

return oXmlDom;

} catch (oError) {

//ignore

}

throw new Error(“MSXML is not installed on your system.”);

} else if (document.implementation && document.implementation.createDocument) {

//DOM-specific code

} else {

throw new Error(“Your browser doesn’t support an XML DOM object.”);

}

That’s all you do for this to work in IE. The more complicated part has to do with Mozilla.

The Mozilla branch

The first step in the Mozilla branch is to create the XML DOM object using